A set of six rII deletion mutants were crossed with each other in all possible combinations with the following results ( + = recombinants produced, i.e., able to grow on E. coli strain K; 0 = no recombinants).

A liquid culture of E. coli strain B is coinfected with equal numbers of two rII point mutants of T4: rII-7 and rII-38. Suspensions of progeny phage are plated on both strain B (giving 1000 plaques per ml of suspension) and on strain K (giving only 5 plaques per ml of suspension). What is the number of map units between site "7" and site "38"?

Various pairs of rII mutants or T4 were tested in both cis and trans positions in E. coli stain K and comparisons made as to the average number of phage particles produced per bacterium ("burst size"). One set of hypothetical results for 4 different rII mutants, r1, r2, r3, and r4, is as follows. ( + = wild type; the slash [/]separates loci on different DNA molecules.)